Rotator cuff disease is prevalent in the general population and is a significant cause of shoulder pain and dysfunction in the orthopaedic patient. A large to massive tear of the rotator cuff can lead to chronic pain and loss of function (i.e. motion and strength) through the shoulder. Loss of the normal integrity of the rotator cuff as a result of a massive cuff tear can lead to superior migration of the humeral head and uncoupling of the humeral head with the adjacent glenoid. This uncoupling or incongruency of the glenohumeral (shoulder) joint can cause pain and loss of function. This is a particularly difficult problem in the active person in his/her middle years who may still be working or involved in leisure activities that have a physical demand on the impaired shoulder.
In the older patient, a longstanding massive cuff tear can lead to a secondary osteoarthritis of the shoulder joint referred to as ‘cuff tear arthropathy’. In the sedentary elderly patient with cuff tear arthropathy, a particular type of shoulder replacement, ‘reverse’ shoulder prosthesis can be used to relieve severe pain and restore shoulder function. The reverse shoulder replacement is a complex implant that requires insertion of glenoid and humeral components. However, in the younger, physically active patient, it is desirable to minimize or delay the onset of cuff tear arthropathy. In addition, reverse shoulder replacement in the younger, physically active person may lead to premature failure of the implant and therefore may not be a prudent surgical choice.
Large to massive rotator cuff tears present a surgical challenge and it may not be possible to achieve a competent repair when there is a lack of residual tendon (cuff), poor quality of remaining tendon or inelasticity (immobility) of the muscle/tendon unit. These large tears that cannot be repaired, or that recur after initial repair, present a significant treatment challenge. Some surgical solutions have included various ‘patches’ to cover the defect, tendon transfers (eg. latissimus dorsi) and prosthetic shoulder replacements. These surgeries can be complex with less than optimum outcomes.
A number of implants have been described which reduce ‘superior’ migration of the humeral head in the patient with a rotator cuff tear. U.S. Pat. No. 6,712,854 B2 and US Patent Application No. 2007/0078477A1 disclose spacers that are adfixed to the overlying acromium and are designed to prevent superior migration. However these implants are adfixed to the relatively thin acromium which could lead to inadequate initial fixation, premature loosening of the implant, or catastrophic fracture and or bone loss of the acromium.
US. Patent Application No. 2011/0178603 A1 discloses an orthopaedic shoulder implant that is configured to be positioned at the midpoint of the glenoid above the superior surface of the glenoid. Stable fixation of the implant requires placement of a bore hole and insertion of a pin (screw) through the superior surface of the glenoid and into the base of the coracoid. Loosening of this implant or later removal of a well fixed implant with associated cement can lead to glenoid bone loss and substantially compromise stable insertion of a future glenoid prosthesis which is required with a reverse shoulder replacement or other type of ‘total’ shoulder replacement. In addition, this acromial spacer is composed solely of a polymer (e.g. high density polyethylene) and would not allow for biologic fixation of the implant to host bone of the scapula.
It is an object of the present disclosure to obviate or mitigate at least one disadvantage of previous shoulder implants.